Room temperature spontaneous valley polarization in two-dimensional FeClBr monolayer

The valley degrees of freedom of Bloch electrons provide a proper platform to realize information storage and processing. Using first principles calculations, we propose that the FeClBr monolayer is a ferromagnetic semiconductor with spontaneous valley polarization owing to the combined effect of magnetic exchange interaction and spin-orbit coupling effect. The FeClBr monolayer shows perpendicular magnetic anisotropy, a high Curie temperature of 651 K and a large valley splitting of 188 meV, which are beneficial for the practical applications in valleytronics. Then, the anomalous valley Hall effect can be realized under an in-plane electrical field due to the valley-contrasting berry curvature. According to the optical selectivity rule, the different valleys at K and K^- points in momentum space can be excited by the circularly polarized light in honeycomb structures; however, the FeClBr monolayer can also respond to the linear light. Therefore, the valley degree of freedom of the FeClBr monolayer can be modulated by circularly polarized light, linear light and hole doping. Our work enriches the library of valley materials and provides a candidate for the study of spintronics and valleytronics field.